1. Field of the Invention
The present invention relates to a heatsink for dissipating heat from integrated circuits or other electronic devices and, more particularly, relates to a removable heatsink capable for providing varying amounts of power dissipation.
2. Description of Related Art
Heatsinks are important components in integrated circuits and other electronic packaged devices which consume power and generate heat. The heatsink draws heat away from the electronic device it is attached to and dissipates the heat into the surrounding environment. Typically, the heatsink will be affixed to an electronic device at the package level. For example, in the case of an integrated circuit, the heatsink is usually attached when the integrated circuit is coated with plastic, metal, ceramic, or otherwise packaged. In the remaining discussion and throughout this specification, integrated circuits will be referred to as exemplary electronic devices to which the present invention relates. However, it should be understood that the discussion also applies to other types of packaged electronic devices.
An integrated circuit should employ a heatsink capable of dissipating the heat that is generated when the integrated circuit is operating at maximum power consumption. Such heatsinks, however, are larger than they might otherwise be since a particular board application for an integrated circuit might generate less heat than the same integrated circuit would generate when operating at maximum power. Attaching a heatsink at the package level is therefore inflexible and inefficient in that the size of the heatsink cannot be tailored to the needs of a particular application. Furthermore, installing the heatsink prior to production of circuit boards or other devices which incorporate integrated circuits may needlessly increase the cost of the devices as well as make them more difficult to handle and process. Permanent heatsink attachment methods using glue or epoxy require additional curing steps and cannot be readily removed after attachment.
The above problems with conventional heatsinks have created a need for removable heatsinks so that different sized heatsinks can be quickly and conveniently applied to integrated circuits as appropriate to a particular application. Various removable heatsinks exist in the prior art. U.S. Pat. No. 4,716,494, issued to Bright et al., discloses a retention system for a removable heatsink using a spring clip. However, the clip is cumbersome, adds additional weight to the integrated circuit, and requires special adoptive retention projections which must be carefully aligned on the integrated circuit. The clip also has practical drawbacks of taking up unnecessary space and potentially leading to damage of the integrated circuit due to excessive force exerted by the spring.
U.S. Pat. No. 4,729,426, issued to Hinshaw, discloses a bonded clip heatsink incorporating a clip of resilient material which is bonded to the heatsink body and adopted to grip the electronic device packaged to secure the electronic device. The clip is cumbersome, takes up unnecessary space and is not truly removable.
U.S. Pat. No. 4,978,638, issued to Buller et al., discloses a method for attaching a heatsink to a plastic package integrated circuit. However, Buller requires the additional step of gluing the heatsink or its mount onto the package. The method disclosed therein is not readily adaptable to other types of electronic device packages, since the mounting means must have a certain amount of resiliency in order for the heatsink to be snapped into place. In addition, the contact between the heat sink and the package is not maintained through the application of downward force, but instead the heatsink is held in place via lateral force.
U.S. Pat. No. 4,712,159, issued to Clemens, discloses a heatsink clip assembly which requires an additional clip and end locking prongs. This assembly is cumbersome, requires unnecessary additional parts and is not easily removable. Furthermore, a non-removable prong platform disposed beneath the integrated circuit is required. All of the above described patents have attendant disadvantages in that they either are not easily removable or require clipping methods which add bulk and unnecessary weight and are therefore not convenient to use within the very tight tolerances of a modern printed circuit board.
As is apparent from the above, there presently is a need for a removable heatsink and heatspreader assembly in which the heatsink can be easily and conveniently removed from the heatspreader. The removable heatsink should permit matching of a desired size and type of heatsink to the performance characteristics of an integrated circuit used in a particular application. The removable heatsink should be easily removable and yet require no additional clips or other parts. Furthermore, the removable heatsink should not violate circuit board tolerance restrictions by taking up additional space on the board, yet should be readily adaptable for use with a wide variety of electronic device packages.